1. Field of the Invention
This present invention relates to the fabrication of integrated circuits. More particularly, this present invention relates to a copper fuse structure in a semiconductor and the manufacture method of the same.
2. Description of the Prior Art
Advances in semiconductor processing technologies, such as high-resolution photolithography and anisotropic plasma etching, are dramatically reducing the feature sizes of semiconductor devices and increasing the device packing density. Unfortunately, as the density of the semiconductor devices increases and the number of discrete devices increases on the chip, the final product yield for many integrated circuit devices (chip yield) can be decreased. For example, one circuit device that experiences this increase in yield loss with the increased circuit elements is the dynamic random access memory (DRAM) currently having 64 megabits of memory on a chip.
One method of overcoming this lower yield on RAM devices is to provide additional rows of memory cells and fusing each row of cells. Currently lasers are used to open the connections (fuses) in the multimegabit RAMs, such as in DRAM or SRAM devices, to disable defective rows of memory cells and to modify the address decoder so that spare rows of memory cells are selected instead.
A structure of a fuse in a semiconductor according to the prior art is shown as FIG. 1. A first inter-metal dielectric layer (IMD layer) 20 is deposited onto a substrate 10. After forming a plurality of openings in the fist IMD layer 20, the first metal plugs 22 and 22a are filled into the openings, as shown in FIG. 1. A secondary IMD layer 24 is deposited onto the first IMD layer 20 and the first metal plugs 22 and 22a. A plurality of holes is formed in the secondary IMD layer 24, wherein each of the holes is formed on each of the first metal plugs, and the first metal layers 26 and 26a are respectively filled into the holes. After repeating the above-mentioned steps, the third IMD layer 28, the secondary metal plugs 30 and 30a, the fourth IMD layer 32, and the secondary metal layers 34 and 34a are formed thereon. Finally, a passivation 36 is deposited onto the fourth IMD layer 32 and the secondary metal layers 34 and 34a, and the passivation 36 is damaged due to an etching process.
In order to couple the secondary metal layer 34 to an external conductive layer, the secondary metal layer 34 has to be exposed after the etching process. On the other hand, the secondary metal layer 34a is the fuse in the above-mentioned semiconductor. Therefore, after the etching process, a thin passivation still has to be retained on the secondary metal layer 34a. For the above-noted object, a well-known method in the prior art is utilizing a first mask for etching the passivation 36 on the secondary metal layer 34 to expose the secondary metal layer 34. The passivation 36 on the secondary metal layer 34a is not removed during the etching process with the first mask. Subsequently, a secondary mask is employed to remove the passivation 36 on the secondary metal layer 34a and keep a thin passivation on the second metal layer 34a. 
In the prior art, the first metal plugs and the first metal layers are consisted of metallic copper, and the secondary metal plugs and the secondary metal layers are made of metallic aluminum. Generally, metallic copper is not preferred to be the composition of the fuse. The reason is that copper is a good material of heat exchange and the uppermost copper layer is usually thick. Consequently, higher energy is necessary during employing a laser repair tool to zip the copper fuse. Because the melting point of aluminum is lower than the melting point of copper, one method for resolving the problem of zipping the copper fuse is replacing the copper fuse with the aluminum fuse. So high energy is not necessary to zip an aluminum fuse. However, the cost of an aluminum fuse is higher than a copper fuse.
Hence, for improving the efficiency in manufacturing the semiconductor and saving the cost of the semiconductor, this present invention provides a copper fuse structure and the method for manufacturing the same.
In accordance with the present invention, a method is provided for fabricating a thin copper metal layer as a fuse in a semiconductor structure so that the copper fuse according to this present invention can be easily zipped by a laser repair tool.
It is another object of this invention to lower the cost of semiconductor manufacturing by utilizing a thin copper metal layer to displace the aluminum fuse in the semiconductor structure according to the prior art.
It is still another object of this present invention to combine the processes for forming an opening on a bonding pad and forming an opening on a fuse of the semiconductor structure. That is, the openings on the bonding pad and the fuse can be formed respectively by an etching process according to this prevent invention. Consequently, the method according to this prevent invention can facilitate the semiconductor manufacture.
In accordance with the above-mentioned objects, the invention provides a structure and fabricating method for a copper fuse in a semiconductor structure. According to this prevent invention, a copper metal layer disposed in an inner layer of a semiconductor structure is employed to be a copper fuse of a semiconductor device. Moreover, an opening on the fuse and an opening on the bonding pad can be formed in the same process, wherein the bonding pad is applied to connect the semiconductor structure and environment. Therefore, it is notably that a copper fuse can be formed effectively and economically in a semiconductor structure according to this present invention.